JP2000117261A - Device for production of electrically deionized water and passing treatment of water through the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regenerate ion exchange membrane without using any liquid chemical agent when hydroxide compounds are deposited on ion exchange membrane being used and accordingly the voltage applied to between an anode and a cathode is increased, and to enable a continuous passing treatment of water through the device by providing the device with a switching means for reversing the passing direction of water through a desalting chamber. SOLUTION: The treatment using this device 30 is performed for an appropriate period, e.g. about two to six months until the quality of treated water approaches to its deterioration point by gradual increase in ions in the treated water and after the treatment, the passing direction of water through a desalting chamber 10 is switched to the reverse direction. The switching operation comprises opening valves 2, 3, 6 and 7; closing valves 1, 4, 5 and 8; supplying raw water to the desalting chamber 10 of the device 30 through a liquid transfer line via the valve 2 to obtain treated water via the valve 3; and also supplying the raw water to a concentration chamber 20 through another liquid transfer line via the valves 2 and 6 to discharge concentrated water via the valve 7. Thus, with such operation, treated water is produced and also, hydroxide compounds deposited on anion exchange membrane, such as calcium hydroxide, are gradually removed from the membrane by acid washing effects of impurity ions in raw water, such as Cl- or SO4-2, to regenerate the anion exchange membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the use of a chemical solution when hydroxide of impurity ions or the like is deposited on an ion-exchange membrane to be used due to long-term water treatment of an electric deionized water producing apparatus. The present invention relates to an electric deionized water production apparatus capable of continuously regenerating the ion-exchange membrane without regenerating the ion-exchange membrane, and a method of treating the water.

[0002]

2. Description of the Related Art In a two-bed, two-bed, three-column or mixed-bed deionized water producing apparatus using a cation exchange resin and an anion exchange resin as ion exchangers, the ion exchange resin used exchanges ions. When the flow-through point is reached, it is necessary to regenerate with an aqueous solution of an acid and an alkali. However, although an ion exchanger is used, an electric deionized water production apparatus which does not require regeneration with a chemical has been put to practical use.

[0003] Conventionally, an electric deionized water producing apparatus which has been put into practical use basically has a mixture of an anion exchange resin and a cation exchange resin as an ion exchanger in a gap formed by a cation exchange membrane and an anion exchange membrane. Filling the ion exchange resin layer to form a desalination chamber, allowing the water to be treated to pass through the ion exchange resin layer, and applying a direct current in a direction perpendicular to the flow of the water to be treated via the two ion exchange membranes. Then, deionized water (treated water) is produced while electrically removing ions in the water to be treated from the concentrated water flowing outside the both ion exchange membranes.

In order to prevent the hardness components of magnesium and calcium present in the water to be treated from depositing on the ion-exchange membrane, the electric deionized water producing apparatus is usually provided with a reverse osmosis membrane apparatus or a hard water softening apparatus. Equipment is installed.

[0005] However, even if a reverse osmosis membrane device or the like is installed in the preceding stage, outflow of magnesium ions or calcium ions of about several tens of ppb to several ppm is unavoidable, and the outflow of this water is carried out for a long period of time. In such an electric deionized water production apparatus, hydroxides of calcium and magnesium gradually accumulate and precipitate in the anion exchange membrane. For this reason,
The electric resistance between the anode and the cathode gradually increases, and a high voltage is required to secure a predetermined current. Further, even if a predetermined current is secured, silica or the like leaks into the treated water, and the quality of the treated water decreases. Conventionally, in order to recover the performance deterioration of such an electric deionized water producing apparatus, the water passing treatment of the apparatus is stopped, and the apparatus is treated with a chemical to elute ions accumulated in the ion exchange membrane. I was trying to recover the device.

[0006]

However, in this chemical cleaning, high treated water quality and low power consumption are required from the viewpoint of maintenance to keep the electric resistance of the stack low in order to secure necessary current. It has to be performed as frequently as the electric deionized water producing apparatus, and for example, there are many apparatuses that operate at a high frequency once a month. In particular, in an electric deionized water production device having a concentrated water circulation structure in which the conductivity of the concentrated water is increased, the electric resistance of the stack is kept low, and high water quality can be obtained with low power consumption, calcium and magnesium in the concentrated water are used. Since the concentration of the hardness component is increased, the above-mentioned precipitation on the ion exchange membrane is likely to occur, and the frequency of chemical cleaning tends to be increased. Further, in the method of treating with the above-mentioned chemicals, a chemical storage tank, piping for chemical cleaning,
Various equipment required for chemical cleaning such as pumps and wastewater treatment equipment must be permanently installed, which not only increases the installation area, but also eliminates the use of chemicals. There was also the problem of extermination. In addition, due to the trend of cost reduction in recent years, it is not preferable to stop the ultrapure water production apparatus for a long time, particularly in the field of semiconductor device production.

[0007] Accordingly, an object of the present invention is to provide a deionized water producing apparatus for a long period of time, through which a hydroxide of magnesium or calcium precipitates on an ion-exchange membrane to be used. It is an object of the present invention to provide an electric deionized water producing apparatus capable of continuously regenerating water while using an ion-exchange membrane without using a chemical solution when a voltage rises, and a method for treating water. .

[0008]

[MEANS FOR SOLVING THE PROBLEMS] Under such circumstances, the present invention
As a result of intensive studies, the clear person has found that
In the long-term water flow treatment of the
Of magnesium and calcium hydroxides
Deposition is performed on the anion exchange membrane located on the outlet side of the concentration chamber.
Occurs on the ion-exchange membrane located on the inlet side of the concentration chamber.
And therefore desalination of the electric deionized water production equipment
If the direction of water flow in the room is reversed and water is passed, it will be on the inlet side
The precipitate on the anion exchange membrane is composed of C contained in raw water.
l^-1, SO_Four ^-2So-called acid due to impurity ions such as
Washed and removed from the anion exchange membrane without using chemicals
Accumulated ions can be removed, and if this is done alternately,
Process water can be obtained continuously without stopping the ion production equipment.
The present invention has been completed, and the present invention has been completed.

That is, the present invention provides an electric deionized water production system in which a cation exchange membrane and an anion exchange membrane are alternately arranged between an anode and a cathode, and a desalination chamber and a concentration chamber are alternately formed between both membranes. The present invention provides an electric deionized water producing apparatus, comprising a switching means for reversing the direction of water flow in the desalting chamber.

The present invention also relates to a water-passing treatment method for obtaining treated water by passing raw water through an electric deionized water producing apparatus, wherein the water flowing direction of the desalting chamber of the electric deionized water producing apparatus is changed. The present invention also provides a method for passing water through an electric deionized water producing apparatus, characterized in that the water is inverted and passed periodically or irregularly.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as raw water,
There is no particular limitation, and examples thereof include well water, industrial water, washing wastewater of semiconductor devices in a semiconductor manufacturing plant, or water obtained by treating these with a reverse osmosis membrane device or a water softening device.
The raw water contains strong electrolytes such as calcium ions, magnesium ions, sodium ions, potassium ions, chloride ions, and sulfate ions, and carbonates, and weak electrolytes such as silica, which are removed by the electric deionized water production apparatus of the present invention. And other impurities.

The electric deionized water producing apparatus used in the present invention is not particularly limited, and a known apparatus can be used. That is, a gap formed by a cation exchange membrane and an anion exchange membrane is basically filled with a mixed ion exchange resin layer of an anion exchange resin and a cation exchange resin as an ion exchanger to form a desalination chamber, While passing the raw water through the layer and applying a direct current in a direction perpendicular to the flow of the raw water through the both ion exchange membranes, the ions in the raw water flow into the concentrated water flowing outside the both ion exchange membranes. This is for producing treated water (hereinafter also referred to as deionized water) while electrically removing the water.

Specifically, spiral type, concentric type and flat plate type are mentioned. The spiral-type electric deionized water producing apparatus, for example, winds a cation exchange membrane and an anion exchange membrane around a center electrode so that a spiral cross section is formed, and runs a desalination chamber and a concentration chamber along the spiral winding. Siege,
An example is a configuration in which an electrode is arranged outside the wound film (for example, JP-A-6-7645). The concentric electric deionized water producing apparatus includes, for example, a plurality of cylindrical frames having different diameters that support a cation exchange membrane and an anion exchange membrane are concentrically arranged, and the outer periphery of the outer frame is And electrodes are arranged around the inner periphery of the inner frame, and the space formed between the frames is alternately divided into a desalination chamber and a concentration chamber, and the outermost compartment and the innermost compartment are formed. An example of a configuration in which the compartment to be used is a concentration chamber and the desalting chamber is filled with an ion exchanger (for example, see JP-A-9-28)
No. 5790). The flat plate type electric deionized water production device is the most commonly used type, for example, a flat plate desalination chamber, a concentration chamber, a cation exchange membrane and an anion exchange membrane are arranged in parallel and a plurality of them are arranged. A configuration in which an anode chamber and a cathode chamber are arranged at both ends is exemplified.

A flat plate type electric deionized water producing apparatus will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view of the electric deionized water production device, in which the cation exchange membranes 41 and the anion exchange membranes 42 are alternately arranged at a distance.
Every other space formed by the cation exchange membrane 41 and the anion exchange membrane 42 is filled with a mixed ion exchange resin 43 of a cation exchange resin and an anion exchange resin to form a desalination chamber 44. In addition, the part which is not filled with the mixed ion exchange resin 43 formed by the anion exchange membrane 42 and the cation exchange membrane 41 located next to each of the desalting chambers 44 is a concentrating chamber through which the concentrated water flows, as described later. 45.

A deionization module 46 is formed by the cation exchange membrane 41, the anion exchange membrane 42, and the mixed ion exchange resin 43 filled therein. FIG. 4 shows a state in which a plurality of the deionization modules 46 are arranged side by side with a spacer (not shown) interposed therebetween.
9 and an anode 50 on the other end.
The enrichment chamber 45 is located at the position sandwiching the above-mentioned spacers, and a partition membrane 51 such as a cation exchange membrane, an anion exchange membrane, or a simple membrane having no ion exchange properties is provided on both outer sides of the enrichment chamber 45 at both ends as necessary. And the partition membrane 5
The portions where the two electrodes 49 and 50 come into contact with each other are partitioned as a cathode chamber 52 and an anode chamber 53, respectively.

In order to treat raw water and produce treated water by such an electric deionized water producing apparatus, the following operation is performed. That is, a direct current is passed between the cathode 49 and the anode 50, raw water flows in from the water inlet A to be treated, and electrode water flows from the electrode water inlets C and D, respectively. The raw water flowing from the treated water inlet A flows down each desalting chamber 44 as shown by the solid line arrow, and when passing through the packed bed of the mixed ion exchange resin 43, impurity ions are removed. Obtained from water outlet a. The concentrated water flowing from the concentrated water inlet B flows down each concentration chamber 45 as shown by the dotted arrow, receives impurity ions moving through both ion exchange membranes, and concentrates the impurity ions. Electrode water which flows out from the concentrated water outlet b as water and flows in from the electrode water inlets C and D flows out from the electrode water outlets c and d. By the above operation, the impurity ions of the raw water are electrically removed, and pure water (treated water) can be obtained.

On the other hand, in this water passing treatment, trace amounts of calcium ions and magnesium ions are deposited on the ion exchange membrane, particularly the anion exchange membrane in the concentrating chamber, even though the impurity ions are electrically removed (eluted). Reacts with OH ^- ions generated by water splitting at the outlet side of, and gradually accumulates and precipitates as insoluble hydroxides, eventually leading to a situation in which the quality of treated water deteriorates. The reason that no precipitate is formed on the inlet side of the anion exchange membrane in the concentration chamber is that a large amount of salts is present in the incoming treated water on the inlet side of the desalting chamber, and the removal of impurity ions is active electrically. This is considered to be because water decomposition hardly occurs and OH ^- ions which react with calcium ions and the like to form insoluble hydroxides are not generated. On the other hand, on the outlet side of the desalting chamber, the salt concentration of water in the desalting chamber is low, and at the same time as removal (elution) of impurity ions, water decomposition occurs to generate OH ^- ions,
It is considered that this reacts with calcium ions or the like to generate insoluble hydroxide on the anion exchange membrane on the side of the concentration chamber.

In the present invention, the timing of switching the water flow direction of the desalting chamber is not particularly limited, but is preferably immediately after or immediately before the quality of the treated water starts to decrease. And method of switching by empirically judging from the capacity of the electric deionized water production apparatus and the method of judging by the resistivity meter or silica meter installed downstream of the electric deionized water production apparatus in the water passage process And the like.

The water passage treatment after switching the water passage direction of the desalting chamber is a treatment for obtaining treated water and electrically regenerating an ion exchange membrane in which calcium hydroxide and the like are accumulated. That is, in FIG. 4, the raw water flows in from the deionized water outlet a (the arrow indicating the water flow direction is omitted in the figure). The raw water flowing from the deionized water outlet a rises in each of the deionization chambers 44 in reverse to the case before the water flow direction switching, and the impurity ions are removed when passing through the packed bed of the mixed ion exchange resin 43. ,
The treated water is obtained from the treated water inlet A in FIG.
At the same time, calcium hydroxide and the like accumulated in the inlet side of the anion exchange membrane 42 (ie, the outlet side of the treated water before switching of the water flow direction) include Cl ^-1 contained in the raw water,
It is so-called acid-washed by impurity ions such as SO ₄ ^-2 and gradually dissolved. Therefore, the anion exchange membrane 42 is gradually regenerated. On the other hand, by the long-term water-flow treatment after the water-flow direction switching, a trace amount of calcium ions and the like become hydroxides and gradually move toward the outlet side of the anion exchange membrane (the side opposite to the deposition site before the water-flow direction switching). It precipitates, and as described above, eventually causes a situation in which the quality of the treated water deteriorates. Then, the same operation is repeated by reversing the flow direction of the raw water in the desalting chamber immediately after or immediately before the quality of the treated water starts to decrease.

In the electric deionized water producing apparatus of the present invention, the switching means for reversing the direction of water flow in the desalting chamber is not particularly limited. For example, the switching means may be any of the following first to third embodiments. The switching means described in the embodiment is exemplified.

(Switching Means in First Embodiment) The switching means of the electric deionized water producing apparatus according to the first embodiment of the present invention will be described with reference to the block diagram of FIG. In FIG. 1, the switching means of the electric deionized water producing apparatus is provided with a piping system and a valve capable of reversing a treated water inlet for supplying raw water to a desalination chamber and a treated water outlet for discharging treated water. . In the first embodiment, the water flow direction of the condensing chamber is simultaneously switched with the water flow direction of the desalination chamber. In FIG. 1, the electric deionized water producing apparatus 30 is schematically shown by a desalting chamber 10 and a concentrating chamber 20. In FIG. 1, the water passing step is performed as follows. First, valve 1,
With the valves 4, 5, and 8 opened and the valves 2, 3, 6, and 7 closed, the desalination chamber of the electric deionization production apparatus 30 is supplied with raw water through a liquid feed pipe passing through the valve 1. 10 to obtain treated water via the valve 4. At this time, the water flow direction of the desalination chamber 10 is rightward in the figure. Raw water is supplied to the concentration chamber 2 of the electric deionization production apparatus 30 by a liquid feed pipe passing through the valves 1 and 5.
It is also supplied to 0 and discharged via valve 8. At this time, the water flow direction of the concentration chamber 20 is rightward in the figure. Although the impurity ions in the raw water are removed by the water passing treatment, on the other hand, as described above, the hydroxides of calcium and magnesium are gradually accumulated at the outlet of the anion exchange membrane in the concentration chamber.
The water passage treatment is performed for an appropriate period of about two months to half a year, for example, until a point at which the quality of the treated water decreases due to the accumulation of the ions. Next, after the water passing process, the water passing direction of the desalting chamber is switched. The switching is performed by valve 2, valve 3,
With the valves 6 and 7 opened and the valves 1, 4, 5 and 8 closed, the raw water is supplied to the desalination chamber 10 of the electric deionization production apparatus 30 by a liquid feed pipe passing through the valve 2. Then, treated water is obtained via the valve 3. At this time, the water flowing direction of the desalination chamber 10 is as shown in the figure.
It is facing left. The raw water is also supplied to the concentration chamber 20 of the electric deionization manufacturing apparatus 30 by a liquid feed pipe passing through the valves 2 and 6, and is discharged through the valve 7. At this time, the concentration room 20
Is directed leftward in the figure. By such an operation, treated water is obtained, and Cl ^-1 in raw water as described above,
Acid cleaning action by impurity ions such as SO ₄ ^-2
Calcium hydroxide and the like are gradually removed from the anion exchange membrane, and the anion exchange membrane is regenerated. Hereinafter, the same operation is repeated. In the first embodiment,
It is easy to regenerate the ion exchange membrane without using a chemical solution. Therefore, separate preparation and supply operations of the chemical solution are not required. In addition, continuous supply of treated water is possible.

(Switching Means in Second Embodiment) The switching means of the electric deionized water producing apparatus according to the second embodiment of the present invention will be described with reference to the block diagram of FIG. In the second embodiment, the direction of water flow in the desalting chamber is switched, but the direction of water flow in the concentration chamber is fixed. 2 is different from FIG. 1 in that the concentrated water flow system has a concentrated water circulation structure that circulates while discharging a part of the concentrated water. Same as 1. In the figure, the concentrated water supplied to the concentration chamber is preferably water to be treated or storage tank water storing the water to be treated.

(Switching Means in Third Embodiment) The switching means of the electric deionized water producing apparatus according to the third embodiment of the present invention will be described with reference to the block diagram of FIG. In the third embodiment, a three-way valve is used as the valve, and the water flow direction of the condensing chamber is simultaneously switched with the water flow direction of the desalination chamber. In FIG. 3, the water passing step is performed as follows. First, the valve 9 is switched to the liquid feed pipe 101 side, and the raw water is supplied to the desalting chamber 10 of the electric deionization production apparatus 30 through the flow path passing through the valve 9 and the liquid feed pipes 101 and 102. The treated water is obtained from the outlet pipe 105 via the valves 103 and 104 and the valve 11. It is needless to say that the valve 11 is switched so that the treated water flows from the liquid sending pipe 104 to the outflow pipe 105. At this time, the water flow direction of the desalination chamber 10 is rightward in the figure. On the other hand, the raw water is also supplied to the concentration chamber 20 of the electric deionization apparatus 30 through a flow path passing through the valve 9, the liquid supply pipe 101, the valve 12, and the liquid supply pipe 108, and the liquid supply pipe 109, the valve 13, and the The liquid is discharged from the discharge pipe 111 via the liquid pipe 110. At this time, the water flow direction of the concentration chamber 20 is rightward in the figure. Next, in order to switch the water flow direction of the desalting chamber, the valve 9 is switched to the liquid supply pipe 106 and the valve 11 is switched to the liquid supply pipe 107 so that the raw water passes through the liquid supply pipes 106 and 103. The water is supplied to the desalting chamber 10 of the electric deionization production apparatus 30 through the flow path, and treated water is obtained from the outflow pipe 105 via the liquid feeding pipes 102 and 107 and the valve 11. At this time, the water flow direction of the desalting chamber 10 is leftward in the figure. On the other hand, raw water is supplied by the valve 9 and the liquid supply pipe 1
06, the flow through the valve 13 and the liquid supply pipe 109 is also supplied to the concentration chamber 20 of the electric deionization production apparatus 30,
Discharge pipe 1 via liquid supply pipe 108, valve 12 and liquid supply pipe 112
It is discharged from 11. At this time, the water flow direction of the concentration chamber 20 is leftward in the figure. The second and third embodiments also have the same effects as the first embodiment.

In the method for passing water of the electric deionized water producing apparatus according to the present invention, the raw water is passed through the electric deionized water producing apparatus, so that calcium ions, magnesium ions, sodium ions, potassium contained in the raw water are contained. Impurity ions such as strong electrolytes such as ions, chloride ions and sulfate ions, and weak electrolytes such as carbonate ions and silica can be removed, and high-quality pure water can be obtained. On the other hand, in the long-term water-flow treatment, the deionized water is passed through the electric deionized water production device in which hydroxides of calcium and magnesium are deposited and accumulated on the anion exchange membrane at the outlet side of the concentration chamber. By inverting the water direction, the precipitate on the anion exchange membrane on the inlet side is so-called acid-washed by impurity ions such as Cl ^-1 and SO ₄ ^-2 contained in the raw water, and a chemical solution is used. Without deposits from the anion exchange membrane. Therefore, regeneration of the ion exchange membrane can be achieved without using a chemical solution, and treated water can be continuously supplied without stopping the apparatus.

[0025]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but this is merely an example and does not limit the present invention. Example 1 Using an electric deionized water producing apparatus having a structure shown in FIG. 4, raw water was subjected to an electric deionization treatment according to the flow shown in FIG. 1 under the following operating conditions and the above operating method. During the operation period, the operation for switching the water flow direction of the desalting chamber was performed once because of the time. As a result, it was possible to obtain desalinated water (pure water) having a resistivity of 17 MΩ · cm continuously over a total period of 4 months including the first water passage treatment period and the water passage treatment period after switching the water passage direction. . During this time, the silica concentration of the treated water is up to 35 ppb
And the DC applied voltage was 325 V at the maximum. In addition,
The silica concentration of the treated water at the beginning of the operation was 30 ppb.

(Operating conditions) ・ Raw water; city water treated with reverse osmosis membrane ・ Electric deionized water production equipment; EDI-010 type (manufactured by Organo Co., Ltd.) ・ Flow rate of water flow: 2 m ³ / hour ・ First Water treatment period: 2 months ・ Water treatment period after switching water passage direction: 2 months ・ Current: 2.0A ・ DC applied voltage: 300V

Comparative Example 1 The same method as in Example 1 was followed, except that the water-passing treatment was performed continuously without switching the water-passing direction. The results are a three-month water treatment period, a resistivity of the treated water of 5 MΩ · cm, a silica concentration of the treated water of 100 ppb, and a DC applied voltage of 550 V.
Met. Therefore, when the electric deionized water producing apparatus was disassembled and examined, a white precipitate was observed on the anion exchange membrane on the outlet side of the concentration chamber. This was found to contain calcium hydroxide as a result of analysis.

[0028]

According to the method of the present invention, impurities consisting of hydroxides of calcium and magnesium are accumulated in the ion exchange membrane to be used by long-term water passing treatment of the electric deionized water producing apparatus. In this case, the ion exchange membrane can be regenerated without using a chemical solution. Therefore, separate preparation and supply operations of the chemical solution are not required. In addition, since treated water (demineralized water) can be continuously obtained, it is possible to eliminate a decrease in the operation rate due to a stoppage of the supply of ultrapure water, particularly in the semiconductor device manufacturing field.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a flow-through treatment method using a switching means of an electric deionized water producing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a water passage treatment method using a switching unit of an electric deionized water production apparatus according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a flow-through treatment method using a switching means of an electric deionized water producing apparatus according to a third embodiment of the present invention.

FIG. 4 is a schematic sectional view of an electric deionized water producing apparatus used in the present invention.

[Explanation of symbols]

 1-8 Two-way valve 9,11-13 Three-way valve 10,44 Deionization chamber 20,45 Concentration chamber 30 Electric deionized water production device 41 Cation exchange membrane 42 Anion exchange membrane 43 Mixed ion exchange resin 49,50 Electrode 101 To 104, 106 to 110, 112 Liquid supply pipe 105 Outflow pipe 111 Drain pipe

Continued on the front page F term (reference) 4D006 GA17 HA47 HA61 JA43Z JA44Z KA01 KA26 KA64 KB11 KC03 KC13 KE13P KE19P PA01 PB02 PB08 PB23 PB27 PB28 PC01 PC02 4D061 DA01 DA02 DA08 DB14 DB19 DC19 EA02 EB01 EB02 EB01 EB04

Claims (2)

[Claims] 1. An electric deionized water producing apparatus comprising a cation exchange membrane and an anion exchange membrane alternately arranged between an anode and a cathode, and a desalination chamber and a concentration chamber alternately formed between both membranes. An electric deionized water producing apparatus, comprising switching means for reversing the direction of water flow in the desalting chamber. 2. In a water treatment method in which raw water is passed through an electric deionized water producing apparatus to obtain treated water, the water flowing direction of a desalting chamber of the electric deionized water producing apparatus is periodically or irregularly changed. A method of passing water through an electric deionized water producing apparatus, characterized in that the water is periodically inverted and passed.